1. Field of the Invention
The invention relates in general to a semiconductor structure, and more particularly to a semiconductor structure with electrostatic discharge protection.
2. Description of the Related Art
In general, integrated circuits (ICs) are susceptible to the electrostatic discharge (ESD) and damaged by the ESD such as the high-voltage transient of an electronic device. In some electronic devices, the high-voltage transient could be have positive and/or negative peaks, and the high-voltage transient may range from hundreds to thousands of volts (V) of static voltage, and the duration may last for several micro-seconds. The high-voltage electrostatic discharge transient could be caused by the user's electrostatic discharge, for example, when the user contacts the terminals or circuits of the integrated circuits (such as apparatus control) or the casing of an apparatus through friction or sensing. Thus, the static voltage caused by negligence may damage the input transistor.
The integrated circuits normally need electrostatic discharge protection circuit to protect the electronic components of an electronic device. However, conventional electrostatic discharge protection structure, such as a high-voltage diode, the voltage is too high and the conducting impedance is too large. Thus, when the voltage increases, the increase in the current is very tiny, and the expected levels of the operating voltage and the current of the high-voltage diode cannot be reached.
FIG. 1 shows a semiconductor structure of generally known technology. The semiconductor structure 5 comprises a substrate 50, an N-type deep well 55, a P-type deep well 60, an N-type deep well 65, an N-type doping well 70, a P-type doping well 75, an insulating material 80, a high-voltage 90 and a low-voltage 95. In terms of location relationship, the N-type deep well 55 is formed in the substrate 50, the P-type deep well 60 is formed in the N-type deep well 55, the N-type deep well 65 is formed in the P-type deep well 60, the P-type doping well 75 is formed in the P-type deep well 60, and the N-type doping well 70 is formed in the N-type deep well 65, wherein, the high-voltage 90 is connected to the N-type doping well 70, and the low-voltage 95 is connected to the P-type doping well 75.
Given that the area is 95 um×150 um, the experimental results obtained according to the generally known technology are illustrated in FIG. 2. FIG. 2 shows a current-voltage relationship diagram of a semiconductor structure of generally known technology. As indicated in FIG. 2, the breakdown voltage is 30V, and the slope of current vs. voltage is very small, and 10V increase in the voltage only leads to 0.3 A increase in the current. The small slope is ascribed to the parasitic resistance of the structure of generally known technology being too larger. Moreover, the human body model of structure of generally known technology is 0.5 KV, which is far below the standard (at least 2 KV) of the integrated circuits.